I think the favor system in this game is pretty clever.  Normally something like this is horrible, players who play for a long time get a big advantage over newbies.  However, this system is implemented in a way where a player can be quickly up to par in about 500 favor and if they make a mistake 1-2 quick games can fix it.  At the same time it encourages players to stick around to get their favor.  It takes the hook of a leveling system and minimizes the downside.

I think this system could be expanded to further exploit a newbie's love for the carrot on the stick.  One of DotA's (and other games similar) biggest problems was rage quitters.  They die and quit and now one team is down a player.  Other players are likely to quit and very quickly you lose the mass of players needed to have an acceptable game.  However, if there are favor rewards that said players are grinding for they are more motivated to stay in the game and much less likely to rage quit.

I think the favor system could be expanded to have favor rankings (all time, weekly, monthly) and have a number of very costly, but purely aesthetic rewards.  These should obviously have no affect on game play, but a system of shiny rewards to grind for could really help keep the players prone to quitting in game.  Sure most if it would mean nothing, but look at gamer score on x-box, it it purely a number and people love it.  Yes, it might make some players favor whores.  I think the players prone to screw their team for more favor would be player who would screw their team in some other way if they didn't have favor to grind for.  At least a lot of the favor titles at the end require somehow contributing to the team.